Glyphosate is a broad-spectrum non-selective herbicide. Since glyphosate has a low solubility in water (12 g/L, 25° C.), in practice, glyphosate is generally formulated into a water-soluble salt. The soluble salts of glyphosate most widely applied at present are mainly isopropyl amine salt, ammonium salts, potassium salt, dimethylamine salts and so on, wherein the dimethylamine salt of glyphosate is the species having the best herbicidal effect and broadest global application among the soluble salts of glyphosate.
A dimethylamine salt of glyphosate generally refers to the monodimethylamine salt of glyphosate which has the following chemical formula:

The formulations of the salts of glyphosate now are still mainly the aqueous formulations. Since aqueous formulations contain a large amount of water, there is much inconvenience in terms of packaging, transportation, storage and so on, and in the meantime, the costs increase. As the market develops and has the increasing demands, there are more and more urgent technical requirements for producing solid formulations with a high content of the glyphosate salts.
At present, the glyphosate salts suitable for the production of solid formulations are mainly the ammonium salts of glyphosate, and the ammonium salts of glyphosate are usually used to prepare the solid formulation products of glyphosate salts, and the industrialized production of granules has been accomplished.
There are only the aqueous formulations at present as the formulations of dimethylamine salt of glyphosate, and it is one of the major aqueous formulation products of US DOW AGROSCIENCES LLC. Up to now, there have not been the relevant reports about a solid formulation of dimethylamine salt of glyphosate.
The Chinese patent application CN 99119971.5 filed by the present applicant discloses a process of industrially producing ammonium salt granules of glyphosate with glyphosate as the starting material, which comprises: to a pressure pan equipped with a stirrer, glyphosate is added, while liquid ammonia is also introduced for reaction, and the weight ratio of glyphosate to liquid ammonia is 1:0.5-1:5; the reaction heat is removed during reaction in time; after the completion of the reaction, the bleeder valve is opened so that the product, ammonium glyphosate, is pressed into a pressure relief tank for granulation to prepare the granules of ammonium glyphosate.
The Chinese patent application CN 00125934.2 filed by the present applicant discloses a process: the solvent, an alcohol, an ether, an aromatic hydrocarbon, an alkane or an organic solvent-water mixture with a water content of less than 25% (w/w) is added to a reactor, and glyphosate and ammonia gas are also added for reaction at a temperature of 10-50° C.; the reaction mixture is cooled to 15-20° C., and then the precipitated crystals are taken therefrom and dried to obtain the product, ammonium glyphosate.
The Chinese patent application CN 02141788.1 filed by the present applicant discloses a process for producing ammonium glyphosate by a gas-liquid-solid three phase reaction, which comprises: glyphosate and water are added to a reactor equipped with a stirrer, and then ammonia gas is introduced for reaction; after the completion of reaction, an aqueous solution of ammonium glyphosate is formed; the solubility of ammonium glyphosate in this system is reduced by the way like adding a water-soluble organic solvent such as methanol, ethanol or methylal into the system so as to precipitate the crystalline solid ammonium glyphosate.
The Chinese patent application CN 200610154750.X filed by the present applicant discloses a process: a soluble salt and a suitable amount of water are added into a reactor at first; the solution is sufficiently stirred to dissolve the salt and then to the salt solution, glyphosate is added and the mixture is stirred to evenly disperse the glyphosate; the reaction temperature is controlled; isopropyl amine is added; after the completion of the reaction, a solid isopropyl amine salt of glyphosate is obtained by crystallization and filtration.
The Chinese patent application CN 200610154745.9 filed by the present applicant discloses a process: glyphosate and a suitable amount of water are mixed under sufficient stirring, then a base containing potassium cation is added for reaction; the reaction temperature is controlled, and then reduce the temperature, and a potassium salt of glyphosate is obtained by crystallization and another time of drying. Also, a process is disclosed therein: a solid glyphosate and a suitable amount of water are mixed under sufficient stirring, then a base containing potassium cation is added for reaction; the reaction mixture is directly dried to obtain potassium glyphosate.
Although there are a number of methods for producing solid glyphosate salts nowadays, the use of these methods to prepare solid dimethylamine salt of glyphosate in industry has the following difficulties: first, the dimethylamine salt of glyphosate has the solubility in water much bigger than that of glyphosate, and even has a certain solubility in some organic solvents and is not easy to crystallize so that it is also more difficult to search a suitable solvent for precipitating it by crystallization; second, the aqueous solution of the dimethylamine salt of glyphosate has a very high viscosity and is characterized in forming gel when it achieves a higher concentration, which causes considerable difficulties in its precipitation by crystallization.
In light of the technical difficulties and problems in the prior art as mentioned above, the present inventor has conducted the investigations deeply and carefully to obtain a crystalline dimethylamine salt of glyphosate and its industrial production process, and a solid herbicidal composition and formulation containing said crystal, and thus fulfills this invention.